1 Neurotransmission

2 How neurons communicate zNeurons communicate through an electrical signal called the Action Potential zAction Potentials may be triggered by sense organs or by other neurons zAn action potential is an all-or- nothing event

3 When does a neuron fire? zNeurons receive neurotransmitter signals through dendrites zSome signals are excitatory (accelerator), some are inhibitory (brake) zIf the combined signals reach the “threshold”, it will trigger the action potential

4 Action Potentials zThe neuron is electrically charged with positive and negative ions both inside and surrounding the cell zIf the threshold is reached, the neuron “fires”, moving ions in and out of the cell and generating an electric impulse which travels down the axon

5 Action Potentials zWhen an Action Potential occurs, a molecular message is sent to neighboring neurons yNeurotransmitters leave the Terminal Buttons and are collected by neighboring dendrites zAfter this happens, the ions and neurotransmitters move back to their starting positions, and the neuron is at rest again

6 Myelin Sheath & Nodes of Ranvier zIf an axon is myelinated (has a myelin sheath), the action potential will jump directly from node to node, without having to actually travel the whole axon. Myelin Sheath

7 Neuron to Neuron zAxons branch out and end in buttons near dendrites of neighboring cells zA gap separates the terminal buttons from dendrites zGap is the “Synapse” Cell Body Dendrite Axon

8 Synapse zaxon buttons contain small storage sacs called synaptic vesicles yvesicles contain neurotransmitters Sending Neuron Synapse Axon Terminal

9 Neurotransmitter Release zAction Potential causes vesicle to open zNeurotransmitter released into synapse zLocks onto receptor molecule in dendrite of adjacent neuron zNormal psychological (and physiological) functioning is dependent on neurotransmitter activity zCan be affected by factors such as disease and drugs

10 Locks and Keys zNeurotransmitter molecules have specific shapes zReceptor molecules have binding sites of the same shape

11 Some Drugs work on receptors zSome drugs are shaped like neurotransmitters zAntagonists : fit the receptor but poorly and block the NT ye.g. beta blockers zAgonists : fit receptor well and act like the NT ye.g. nicotine.

12 Further research zWe have covered a lot of material already in this unit and there is more to come! zMake sure you understand what we are doing as we go along! zYou can come in for tutoring after school M- Th, I am here most days until at least 3:30. zFor this material, check nt/psychsim/index.htm (site is listed in your packet) – Quiz next class! nt/psychsim/index.htm